Detached eddy simulation of flow through a circular patch of free-surface-piercing cylinders

The study carried out a numerical investigation of the open channel flow through a circular array of cylinders piercing the water surface. Unlike a lot of the previous research, this study took into account the influence of the bed friction and free water surface. A Zonal Detached-Eddy Simulation (ZDES) model was developed to simulate the turbulent free-surface flow. The non-hydrostatic model was discretized using the Finite Volume Method (FVM). Within the patch, each individual cylinder was directly modelled by specifying the no-slip boundary condition at the solid surface. The ZDES model was verified to be able to capture the small scale turbulent coherent structures. The instantaneous and average flow fields were analysed in detail with the aid of streamline visualization and vortex identifying technique (Q-criterion). The investigation shed light on the complex interaction between the free surface flow and the cylinder array arranged into a circular patch. The complexity arises from the interplay among the separated flows from individual cylinders, interference between adjacent cylinders and the bulk porous-media effect of the patch. The study highlighted the dependence of the flow characteristics on the key properties of the patch, especially the Solid Volume Fraction (SVF). The work demonstrated the encouraging capability of the established numerical technique for the investigation of vegetated flows.